Effect of position in the tree and pretreatment of Acacia mangium leaves on rumen dry matter and nitrogen degradabilities

[摘要] ThehypotheseswerethattherelativerateofdegradabilityofAcaciamangiumleavesintherumenwouldbelow;andthatthiscouldbeimprovedbychemicalpretreatmentwithacidoralkali.Intrial1,usinga3x2factorialdesignwiththreereplications(fistulatedsteers),themaintreatmentswereleavestakenfromthebottom(B),themiddle(M)orthetop(T)branchesofAcaciamangiumtrees;thesub-treatmentsweretheabsence(-MUB)orpresence(+MUB)ofamolasses-ureablockinthedietoftheanimalsusedfortheincubations.Thedegradabilityofbothdrymatterandnitrogendecreasedsignificantly(r5=.85,P=.001;andr5=.50,P=.03for-MUB:andr5=.96,P=.001;and.29;P=.13for+MUBrespectively)asthepositionoftheleavesinthetreechangedfromtoptobottom.OverallmeansforDMwere:27.5,25.6and22.7%in48hrandforN,20.5,18.5and16.4%fortop,middleandbottomleaves.DegradabilitiesofDMweresignificantlyhigher(P=.001)insteersreceivingtheMUB(27.6%)thaninthosefedonlyricestraw(22.9);comparablevaluesforNwere:20.2and16.7(P=.01).Valuesfordegradabilitywereingenerallow(maximumof30%fordrymatterand22%forN)consideringtheincubationperiodintherumenwas48h.Intrial2,inafactorialdesign10x2with3replications(animals),themainvariableswerechemicalpre-treatmentoftheleavesofAcaciamangiumasfollows:Control(notreatment),NaOHsolutionsof2%,3%,6%,9%(w/v)inwhichtheleavesweresoakedfor48h,ureasolutionsof3%,6%,9%(w/v)addedattherateof300ml/1kgoffreshleavesandensiledfor7days,Ca(OH)2solutionof10%(w/v)inwhichtheleavesweresoakedfor48h;quot;Aquot;molassesdilutedinwater(1partmolasses:2partswaterv/v)fermentedinopenvesselsfor7daysthenaddedtotheleaves(1.5litresfermentedsolution/10kgfreshleaves)andensiledfor7days.Thesub-treatmentswerethepresence(+MUB)orabsence(-MUB)ofthemolasses-ureablockassupplementtothebasaldietofricestrawthatwasfedtothefistulatedsteers.Theleaveswerecollectedfromthemid-pointof2-year-oldAcaciamangiumtreesandwerecutinto3cmstripspriortobeingtreatedwiththedifferentadditives.Allthechemicalpre-treatmentsincreasedthedegradabilityofbothdrymatterandnitrogencomparedwiththecontrol(P=.001).Therumendegradabilitieswerehigherinthesteershavingaccesstothemolasses-ureablocks.Thehighestdrymatterdegradabilitywaswiththefermentedmolassestreatment(45%)whichwassuperiorby62%comparedwiththecontrol(27.8%)forthe+MUBtreatmentandby58%for-MUB(valuesof37.1and23.5respectively).CorrespondingimprovementsforNdegradabilitywereevenhigherat89and103%,respectively.TherewerelinearincreasesindegradabilityofbothdrymatterandNastheconcentrationofNaOH,orurea,increasedinthetreatmentmedia.TheexperimentalfindingssupportthehypothesesthattherumendegradabilityofleavesofAcaciamangiumislowandthatthiscanbeimprovedmarkedlybychemicalpre-treatment,especiallyCa(OH)2andaceticacid(themainproductofthefermentationofmolasses).

[学科分类] 农业科学（综合）